Coal-fired combustion chambers of the type used in power-generating plants burn dust-like coal fines which are ground or pulverized by an on-site coal mill. It is critical to deliver even, distributed flows of coal fines to the multiple burners in the combustion chamber to prevent "rich" areas in the combustion chamber which produce LOI (loss on ignition) particles; "lean" areas which promote NOX formation; elliptical fireballs, which create uneven heating and fireball impingement on the boiler tube "water walls"; coal falling out of suspension in the delivery pipes, causing spontaneous combustion fires and risk of explosion; and, fireball backup in "light flow" burners, which can seriously damage them.
One prior art device which attempts to provide evenly distributed flows of coal among multiple pipe branches on the way to the burners is the "riffle box", typically a series of alternately-angled plates or bars placed at each branching of the pipes in an attempt to redistribute the heavy and light coal flows or "ropes" which often develop across the delivery pipe. Schematic examples of riffles boxes are shown in FIG. 1.
Riffle boxes have generally been found to be unsuccessful in creating evenly distributed flows of coal in the downstream pipe branches. A significant improvement over riffle box type devices is found in co-pending U.S. application Ser. No. 08/987,646, co-owned with the present application. That application discloses a device which causes heavy and light flows of coal distributed across a pipe to converge upon one another, preferably upstream of the riffle box, causing them to implode and be evenly distributed across the width of the pipe. This device has been found to be particularly useful for round, large-diameter delivery pipes. It is, however, somewhat difficult to fit to rectangular conduits because it requires upstream and downstream rectangular-to-round adapters.